The influence of starvation on respiration (R), dry weight (W), carbon (C), nitrogen (N), hydrogen (H), and energy content (E; calculated from C) of spider crab (Hyas araneus L.) larvae was studied in the laboratory. In all larval stages (zoea I and II, megalopa) W increased during postmoult, independent of food, and decreased subsequently. The final reduction in W after continued starvation increased from stage to stage (9, 13, and 20% respectively) but it was always much lower than the decrease in C (44 to 52%), N (42 to 46%), H (50 to 58%), and E (53 to 62%). Individual (R) and weight-specific respiration rates (QO sub(2)) were reduced by 83 to 88%. The time-dependence of these reductions in metabolism and biomass as well as the rates of change in all parameters studied were described with non-linear regression models and differential equations, respectively. Rates and total amounts of energy lost during starvation were independently calculated from C and R values, and similar results were mostly obtained.